In music, the parallel minor of a particular major key (or the parallel major of a minor key) is the key which has the same tonic and a different key signature, as opposed to relative minor (or major, respectively). For example, G major and G minor have different key signatures (one sharp and two flats, respectively) but both have the same tonic, G; so we say that G minor is the parallel minor of G major.

Easily calculating the parallel major or minor of a key

To find the parallel minor of a key, add 3 flats to the key signature.

For example, F major has 1 flat (B). Adding 3 flats would yield 4 flats, meaning F minor has 4 flats in its key signature. (B E A D)

B major has 5 sharps (F C G D A). To find B minor, add 3 flats. Since flats cancel out sharps, you are left with 2 sharps. (F C)

To find the parallel major, add 3 sharps.

Em to EM: Em has 1 sharp (F). Add 3 to get 4 sharps. (F C G D)

Fm to FM: Fm has 4 flats (B E A D). Add 3 sharps to get 1 flat. (B)